Citizen Science Program Shows Urban Areas Have Lower Occurrence of Frog Species, but Not Accelerated Declines.

Martin J Westgate,Ben C Scheele,Karen Ikin,Don A Driscoll,Laura Rayner,Anke Maria Hoefer,Murray Evans,David Hunter,R Matthew Beaty,Will Osborne,Benedikt R Schmidt

doi:10.1371/journal.pone.0140973

Abstract

Understanding the influence of landscape change on animal populations is critical to inform biodiversity conservation efforts. A particularly important goal is to understand how urban density affects the persistence of animal populations through time, and how these impacts can be mediated by habitat provision; but data on this question are limited for some taxa. Here, we use data from a citizen science monitoring program to investigate the effect of urbanization on patterns of frog species richness and occurrence over 13 years. Sites surrounded by a high proportion of bare ground (a proxy for urbanization) had consistently lower frog occurrence, but we found no evidence that declines were restricted to urban areas. Instead, several frog species showed declines in rural wetlands with low-quality habitat. Our analysis shows that urban wetlands had low but stable species richness; but also that population trajectories are strongly influenced by vegetation provision in both the riparian zone and the wider landscape. Future increases in the extent of urban environments in our study area are likely to negatively impact populations of several frog species. However, existing urban areas are unlikely to lose further frog species in the medium term. We recommend that landscape planning and management focus on the conservation and restoration of rural wetlands to arrest current declines, and the revegetation of urban wetlands to facilitate the re-expansion of urban-sensitive species.

Highlights

The majority of the human population lives in urban areas [1], and the total area devoted to urban land uses continues to rise in many regions of the world [2]
Model selection by AICc showed that complex models were nearly always selected to describe frog population trajectories in our study region, with models that included interactions being strongly weighted for six of eight species, as well as for species richness (Table 2)
Using a long-term citizen science dataset, we have quantified the association between wetland attributes and the distribution and trajectory of frog populations in an urban landscape

Summary

Introduction

The majority of the human population lives in urban areas [1], and the total area devoted to urban land uses continues to rise in many regions of the world [2] This process is considered to be broadly detrimental to biodiversity [3,4], urban areas are capable of sustaining diverse plant and animal assemblages in many instances [5,6]. A valuable goal for ecology is to identify circumstances where landscape planning can be used to facilitate the persistence of threatened or valued animal species in urban and peri-urban areas. This goal requires identification of attributes of those areas (such as the quality and availability of suitable habitats) that are associated with declines or expansions of biodiversity

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Conclusion